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We have ISP link 4x10G LACP Layer2 and now we are upgrade to to 8x10G LACP, currently i have created VLAN interface to terminate that link because it L2

Now i have option to decide to go with L3 or L2, so i have question what is the advantage to use L3 LACP over L2?

If there is no advantage then i can stick to L2 but i would like to know if there is a big advantage of using L3 here.

  • 1
    There is no such thing as "L3 LACP." Based on the context, I am guessing that you are asking if you should configure your LAG interface as a L2 or L3 interface, but that isn't entirely clear. You could also be asking about which type of LAG hashing method to choose, which would help determine the balance of traffic on your LAG. Please clarify your question to allow us to provide better answers to your question. – YLearn Jul 17 '18 at 18:29
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The main issue is not related to LACP, but to how L2 (with SVI) and L3 ports handle spanning tree:

If you configure the link as L2 and configure an SVI, you will be running spanning tree on the Etherchannel (if it is enabled). This could have implications such as a 30 second delay before the Etherchannel transitions to Forwarding when it is brought up. If there is link instability, this would delay the link recovery time each time it bounces. Also consider the STP mode the switch is running. If it operates as CST (STP/RSTP), the Etherchannel may be affected by topology changes elsewhere in the network. Similar can happen with MST if it is sharing an instance with other VLANs. You also risk interacting with the SP's STP (if they haven't disabled). If you use L2, I would recommend disabling STP for the VLAN/Etherchannel and enabling BPDU filter. Alternatively, configure the Etherchannel to be an Edge Port (PortFast).

If you configure the Etherchannel as L3, it will not participate in STP. It will start forwarding as soon as the Etherchannel is brought up and will not be tied to your STP topology or that of your SP. L3 Etherchannel will be a lot more stable without requiring additional configuration.

I would recommend going with an L3 Etherchannel.

  • You have good point there! +1 – Satish Jul 17 '18 at 21:37
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The choice between using a L2 or L3 link is really independent of LACP.

Assuming your LACP hashing algorithm choice uses layer 3 information to choose the link (and your ISP does the same), there is little difference.

  • Ron - could you please provide mode details here so other folks can understand and learn. I totally get it what you trying to say. – Satish Jul 18 '18 at 2:59

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